Semiconductor devices are used in a variety of electronic applications, such as, for example, personal computers, cell phones, digital cameras, and other electronic equipment. Semiconductor devices are typically fabricated by sequentially depositing insulating or dielectric layers, conductive layers, and semiconductor layers of material over a semiconductor substrate, and patterning the various material layers using lithography to form circuit components and elements thereon.
The semiconductor industry continues to improve the integration density of various electronic components (e.g., transistors, diodes, resistors, capacitors, etc.) by continual reductions in minimum feature size, which allow more components to be integrated into a given area. In some devices, multiple dies or packages with active devices or circuits are stacked vertically to reduce the footprint of a device package and permit dies with different processing technologies to be interconnected. Interconnections for this vertical stacking, or for mounting a die or package on a carrier, board or other die, are created by forming redistribution layers (RDLs) with conductive lines in insulating layers. Passivation layers and post-passivation interconnects provide connection between the RDLs and a connector such as a solder ball, stud, bump or the like. The RDLs and passivation layers are frequently formed using back-end-of-line (BEOL) processes after the production of active devices.